1. Field of the Invention
The present invention relates to a linear motion guide unit that guides an object to be moved, and which is equipped on, for example, a machine tool or industrial robot.
2. Description of the Prior Art
An example of this type of linear motion guide unit of the prior art is the linear motion rolling guide unit shown in FIGS. 1 and 2.
As shown in the drawings, the linear motion rolling guide unit has track rail 1, in which tracks in the form of a pair of track grooves la are formed in both the right and left sides along the lengthwise direction, a slider in the form of sliding unit 3 having rolling element circulating path 2 (refer to FIG. 2, to be later described in detail) and able to move relative to said track rail 1, and a plurality of rolling elements in the form of balls 4, that bear the load between track rail 1 and sliding unit 3 by circulating while rolling over the above-mentioned track grooves 1a accompanying movement of sliding unit 3, and which are arranged and contained within said rolling element circulating paths 2.
Sliding unit 3 has casing 6, provided so as to straddle about track rail 1, and seals 8a and 8b provided on the front and back ends of said casing 6. A flat mounting surface 6a for attaching a table to be described later is provided on the top of casing 6, and a plurality of threaded holes 6b are formed in said mounting surface 6a into which bolts 9 for fastening the table are screwed.
In addition, the above-mentioned rolling element circulating path 2 is formed in both the left and right sides of casing 6, and is composed of load bearing track grooves 2a and return path 2b formed linearly and in parallel with each other as shown in FIG. 2, and direction changing path 2c that connects the ends of loading bearing track grooves 2a and return path 2b. The above-mentioned load bearing track groove 2a corresponds to track groove 1a of track rail 1.
Furthermore, grease nipple 10 for supplying grease to the above-mentioned balls 4 is mounted on the side of casing 6.
FIG. 3 shows an example of using a linear motion rolling guide unit having the above-mentioned constitution with track rail 1 positioned vertically.
As shown in the drawing, a pair of vertical supports 13 are provided, and one set each of linear motion rolling guide units are mounted in a state of mutual correspondence. More specifically, as shown in FIG. 1, a plurality of bolt insertion holes 1b are formed at equal pitch in track rail 1. Bolts 14 inserted into bolt insertion holes 1b are then screwed into threaded holes (not shown) formed in supports 13 to fasten supports 13 to track rail 1.
As shown in FIG. 3, table 15 is arranged between both supports 13, and both ends of table 15 are attached to sliding unit 3. More specifically, table 15 is formed so that its overall shape is that of the letter "U". The suspended portions of both ends of table 15 are fastened to mounting surface 6a (refer to FIGS. 1 and 2) of casing 6 equipped on sliding unit 3 by means of bolts 9.
FIG. 4 shows another example of the case of using the above-mentioned linear motion rolling guide unit in a vertical manner.
As shown in the drawing,L-shaped brackets 17 are fastened to casing 6 of each sliding unit 3 in this example. A flat table 18 is then fastened to both of said brackets 17 by means of bolts 19.
As described above, in the case of using the linear motion guide unit of the prior art in a vertical manner, the table to be attached must be formed into a "U" shape, or the table must be attached by means of L-shaped brackets. Thus, the weight of the moving portion that includes the table and brackets increases. As a results it is difficult to improve response characteristics and so on. Also, since the machining accuracy of the U-shaped table and L-shaped brackets must be high to avoid the effect on mounting error by the-right angles of the bent portions of said U-shaped table and L-shaped brackets, manufacturing costs.